1. Field of the Invention
The disclosure is directed to a sniffing leak detector comprising a test gas sensor, and in particular to a sniffing leak detector with a large measurement range of leakage rates.
2. Discussion of the Background Art
Patent Application DE 10 2005 021 909 (not pre-published) describes a sniffing leak detector comprising, for example, a test gas sensor, wherein a sniffing probe is connected to the test gas sensor via a sniffing line. A vacuum pump creates a vacuum in a suction chamber provided in front of the quartz window of the test gas sensor. This sniffing leak detector allows different modes of operation, namely normal, standby, protection against contamination and simulation of a gross leak. In the mode for protection against contamination, a venting valve is temporarily connected to the suction chamber of the test gas sensor, thereby causing a flushing effect.
The conventional analysis apparatus for sniffing leak detection with a high detection sensitivity for helium employs mass-spectroscopy methods for detection. These require high vacuum conditions of p<10−4 mbar. Such pressure conditions are obtained using a pump system requiring a turbomolecular pump. This kind of pump is complex. Further there are sudden failures because of fused filaments of the mass spectrometer.
The Patent Application 10 2005 021 909 mentioned above describes a sniffing leak detector with a test gas sensor adapted to detect helium leakage rates in a range from 10−7 mbar l/s to 10−3 mbar l/s. For smaller leakage rates, the detection range is restricted due to the limited signal stability or the limited sensitivity. For higher leakage rates, the limitation is defined by a possible contamination of the sensor. At a measured leakage rate of 10−3 mbar l/s, the helium partial pressure in front of the sensor is about 0.05 mbar. The sensor must be protected against helium partial pressures above this limit. This is achieved by changing over the gas guide so that, upon exceeding the fixed signal intensity, the apparatus temporarily switches off the detection of helium.
It is an object of the disclosure to provide a sniffing leak detector having a widened leakage rate measurement range.